Jeep Gladiator 100K Maintenance Guide (2020–2025)

Read This Before You Wrench

Before you wrench: This guide outlines common 100K-mile service items for 2020+ Jeep Gladiators. Some maintenance tasks are straightforward, but others — like transmission pan/fluid service, spark plug replacement, brake fluid flushing, differential and transfer case service, and FOX shock rebuilds — require specialized tools, technical skill, and proper safety procedures.

If you’re not fully confident, GladiatorUp recommends using a qualified, independent ASE-certified mechanic who understands 4×4 and off-road platforms. If you choose to DIY, you assume all risk. Always verify torque specs, fluid types and capacities, lift points, and safety steps before beginning work.

GladiatorUp.com assumes no responsibility for damage, injury, or warranty issues resulting from reader-performed maintenance. Work smart. Work safe. Protect yourself — and your Gladiator.

A Jeep Gladiator that hits 100,000 miles isn’t slowing down — it’s just reaching cruising altitude. The JT platform is tough, the 3.6 Pentastar is proven, and the truck rewards owners who give it proactive, thoughtful maintenance. Whether your rig is a commuter, a tow mule, or a Mojave that’s lived its life at speed across desert whoops, 100K is the perfect moment to reset the clock for the next adventure.

This is a real-world, 100K service guide for 2020+ Gladiators with the 3.6L Pentastar — including a dedicated section for Mojave and Rubicon FOX shocks, common Pentastar issues, and what Jeep really means when it says “lifetime” fluid. It is experience based but by no means should be considered authoritative. Consult official maintenance and repair manual sources published by the manufacturer for the latest guidance, practice, and facts concerning any repair or modification.

THE 100,000-MILE SERVICE — WHAT YOU MUST DO

1. Engine Oil & Filter*

Change every 5,000 miles (not 8–10K; Pentastars prefer shorter intervals)
Use 0W-20 full synthetic
Mopar, WIX, or NAPA Gold filters recommended
Listen for early cam lobe wear (warm ticking, random misfires)

2. Spark Plugs (6 total)*

Official interval: 60K
By 100K, replace no matter what
Use OEM Champion ($$), NGK ($$$) or Bosch ($$)
Inspect coil packs while accessible (best to replace, keep takeoffs for spares)

3. PCV Valve*

Replace by 100K
Helps control idle quality and oil consumption
Extremely cheap but often neglected
Mopar only

4. Engine Air Filter*

Replace yearly
If you wheel in dusty Southern trails, replace sooner

5. Cabin Air Filter*

Replace annually
Makes a huge difference for open-top drivers

6. Automatic Transmission Service (850RE 8-Speed)

Jeep markets the 850RE’s fluid as “lifetime,” but that only applies to the warranty window — not high-mileage ownership. The 850RE is a U.S.-built variant of the ZF 8HP, and ZF recommends fluid + filter every 60K–80K miles for heavy-duty use. That’s most Gladiators.

Can you service it?

Yes.
The 850RE requires full pan removal because the filter is built into the pan. There is no drain plug.

A proper service includes:

New transmission pan (integrated filter) – optional
New pan gasket
ATF+9 fluid
Temperature-specific fill and level check

Should you do it at 100K?

If you tow, off-road, live in Southern heat, run big tires, or plan to keep your JT past 120K: yes — service it.
Fresh fluid smooths shifts, lowers temps, and extends lifespan.

If you’re a light highway driver: optional but beneficial.

7. Transfer Case Fluid*

Replace every 60K (or 30–40K in severe use)
At 100K, this should be your 2nd change
Crucial for Rubicon and Mojave models

8. Differential Fluid (Front & Rear)*

Replace every 40K–60K
At 100K, both diffs should be serviced
Use correct friction modifier for locking axles

9. Coolant / Antifreeze Flush*

Jeep says: 10 years / 150K
Real-world experience says: 100K is safer
Keeps water pump and thermostat healthy.

10. Serpentine Belt*

Inspect at 60K
Replace at 100K or sooner if squeaking
Check tensioner roller for wear

11. Brake Fluid Flush

Replace every 2–3 years
If you haven’t done it by 100K, it’s mandatory now

100K-MILE INSPECTION POINTS*

Suspension & Steering

Upper/lower ball joints (common wear item)
Tie rod ends
Control arm bushings
Track bar bushings (especially rear)
Steering stabilizer
Sway bar links

Cooling System

Water pump seepage (pink crust)
Radiator tank cracks
Coolant reservoir
Thermostat housing

Driveline

Driveshaft U-joints
Carrier bearing
Front CV axle boots

Brakes

Pad thickness
Rotor condition
Caliper slide pins (clean & grease)

Electrical

Battery health (4 years = end-of-life)
Ground straps
Corrosion at fuse box
Alternator test

rare / KNOWN 3.6L PENTASTAR ISSUES AROUND 100K

1. Camshaft & Lifter Wear

Symptoms:

Warm ticking
Light misfires
Rough idle after warm-up
Metal sparkle in oil

5K oil intervals dramatically reduce risk.

2. Cylinder 6 Misfire

A common heat-soak problem
Often coil or plug related
Use OEM ignition parts only

3. Oil Cooler / Filter Housing Leaks

All OEM units are plastic
Aluminum OE replacement recommended (Dorman)
Look for oil pooling in the valley, heavy burning oil smell, dripping down rear of engine/trans

4. Water Pump

Typical replacement window: 100K–150K
Watch for smell of coolant or temp spikes

5. Radiator Cracks

Inspect plastic end tanks at 100K
Not as bad as JK era but still happens

MOJAVE & RUBICON FOX SHOCK CARE AT 100K

If you own a Mojave (or Rubicon with FOX-equipped packages), your shocks are wear items, not lifetime parts. FOX recommends rebuilds every 40K–50K miles for off-road use.

1. Inspect All Four Shocks*

Look for:

Oil seepage
Wet shock bodies
Harsh small-bump ride
Sagging front or rear
Clunks or dead zones in the stroke
Excessive brake dive

Any of these = rebuild time.

2. Rebuild vs. Replace

Rebuild (Recommended)

FOX 2.5 internal bypass shocks are designed to be rebuilt
Cost per shock: $125–$175
Bushings/seals: $40–$60
Labor for full set: $300–$350
Shipping: $60 each way

Rebuilding gives you factory ride and control back.

Replace (Optional)

If the bodies are damaged or you want an upgrade:

FOX Factory Race Series 2.5
Falcon 3.3/3.5
Falcon SP 2.1 monotubes (my favorite)
…but for most Mojave owners, a rebuild is most desirable.

3. Hydraulic Jounce Bumpers (Mojave Only)

These can:

Lose nitrogen charge
Seep oil
Collapse internally
Become harsh or bottom out

Rebuild or recharge at the same time as your shocks.

4. Control Arms & Ball Joints

Because the Mojave is tuned for high-speed desert work:

Ball joints wear faster
Control arm bushings fatigue sooner
Track bar bushings can loosen

Inspect at every oil change.

OPTIONAL PREVENTIVE MAINTENANCE AT 100K

Throttle body cleaning
Techron fuel system treatment
Diff breather extensions
Battery cables/ground strap refresh
Wheel bearings (if lifted or on 35/37s)

100K SERVICE — QUICK CHECKLIST

Replace:

Engine oil & filter
Spark plugs
PCV valve
Air and cabin filters
Transmission pan/filter + fluid (850RE)
Transfer case fluid
Differential fluids
Coolant
Serpentine belt
Brake fluid

Inspect:

Suspension & steering
FOX shocks and jounces
Water pump & radiator
Driveshaft joints
Battery & electrical
Brakes

Watch for:

Lifter tick
Cylinder 6 misfire
Oil cooler leaks
Water pump seep
Radiator cracks

bottom line

A well-maintained Gladiator easily crosses 250K miles — especially with a 5K oil interval, fresh fluids, and FOX shock care. Treat your JT right at 100K, and it’ll reward you with reliability, smooth performance, and many more unpaved miles ahead.

Here’s to the road unpaved! – Doug

* = fairly easy DIY

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This guide is for informational purposes only. Always verify procedures with a qualified mechanic. Use at your own risk. GladiatorUp.com assumes no liability for any damage or warranty concerns resulting from the use of this content.